fix: firefox avatar icon styling inconsistency

[GretaD]

the issue on FF only:

what is happening:
In Chromium the base position of the icon horizontally is "middle of the avatar" while in Firefox it is "on the left".

I have no idea, why it shown like that. Looks like it applies justify-self: center; from material-design-icon. But that shouldn't happen. Because it is not in a flex container. Chrome shows a warning that this property cannot be applied. But it is actually applied. Screenshot below.

Then the icon is moved using absolute position (left: 81px). And because the base position is different, it is different afterwards. 81px is a value used relative to chromium's invalid rendering.
The layout is bad in general. ✅ icon and "Invitation accepted" string are children of a small avatar and then moved via position absolute/relative to a fixed place in pixels, paddings are inconsistent as well. I guess we do that, to make it work for an unstable layout.
If we dont want to spend 1h+ debuging very simple things, we should consider redoing it.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 23.41%. Comparing base (c27f067) to head (02e8ed4).
Report is 5 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #6614   +/-   ##
=========================================
  Coverage     23.41%   23.41%           
  Complexity      472      472           
=========================================
  Files           249      249           
  Lines         11899    11899           
  Branches       2268     2279   +11     
=========================================
  Hits           2786     2786           
  Misses         8786     8786           
  Partials        327      327           

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[ChristophWurst]

No backport necessary because #6580 wasn't backported either